Zebrafish (Danio rerio) as a Model for the Study of Glial Calcium Signaling in Awake, Behaving Animals
Glial biology has been studied for over a century, yet the existence of dynamic calcium signaling in astrocytes was only discovered in 1990. Early studies used cultured astrocytes to investigate this phenomenon; however, studies in cultured cells are highly vulnerable to artifactual results that do not accurately represent normal physiological conditions. More recent studies in vivo have revealed a broad heterogeneity in astrocyte signaling—the mechanisms that trigger a calcium rise, the sources of that calcium rise, and the downstream effects of astrocyte signaling all vary with different brain regions and types of stimulation. In zebrafish (Danio rerio), the primary glial cell type is radial glia that persist into adulthood, which have previously been shown to perform many of the same roles as mammalian astrocytes, including regulating synaptic glutamate uptake and maintaining CNS water balance. This study establishes that zebrafish are an appropriate model for studying glial calcium signaling, which can be triggered by eliciting an acoustic startle response in awake, behaving fish. The glial calcium signal, measured by the genetically encoded calcium indicator GCaMP5, reliably peaks following an escape response and is mediated by the group I metabotropic glutamate receptor mGluR1.